import math
a = float(input())
b = float(input())
pi = 3.1415926
r = ((a/2)**2+b**2)/(2*b)
#角c
c = 2*math.asin((1/2)*a/r)
sector = (c/(2*pi))*r**2*pi
triangle = (1/2)*r**2*math.sin(c)
print(f"{sector-triangle:.2f}")